While Ulliminik(sp? >.>) is still a pain despite the update.. making the Trigger item Ex/rare wouldn't help.
Nothing would stop the gilseller to simply claim the NM, kill it and sell the Trigger to the highest bidder while it is still in the treasure pool. Kinda like how BB items are sold.
Further more... making Trigger Ex would only make much more harder popping the actual gods, since the same person must be present to get the 2 pop items and be there to pop.
The real solution to the problem is still hard to find however. A System similar to Olla (with some adaptation to the room/type of mob) could work.